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Semiperfect number
In mathematics, a semiperfect number or pseudoperfect number is a natural number n that is equal to the sum of all or some of its proper divisors.
The first few semiperfect numbers are 6, 12, 18, 20, 24, 28, 30, 36, 40, ... ; every multiple of a semiperfect number is semiperfect, and every number of the form 2mp for a natural number m and a prime number p such that 2m < p < 2m + 1 is also semiperfect.
A semiperfect number that is equal to the sum of all its proper divisors is called a perfect number; an abundant number which is not semiperfect is called a weird number.
See also
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12-03-2008 10:22:39
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The contents of this article is licensed from www.wikipedia.org under the GNU Free Documentation License. Click here to see the transparent copy and copyright details